1. Field of the Invention
The invention generally relates to mobile communication technologies, and more particularly, to buffer status reporting methods for machine type communication data transmission and related mobile communication devices.
2. Description of the Related Art
In a typical mobile communications environment, a user equipment (UE) may communicate voice and/or data signals with one or more service networks via cellular stations (or referred to as evolved Node-Bs (eNBs)) of service networks. The wireless communications between the UE and the service networks may be in compliance with various wireless technologies, such as the Global System for Mobile communications (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, Code Division Multiple Access 2000 (CDMA 2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, and others.
According to the UE medium access control (MAC) specification, a Buffer Status Report (BSR) provides the serving cellular station with information about the amount of data available for transmission in an uplink (UL) transmission buffer of the UE. There are three types of BSRs, regular BSR, periodic BSR and padding BSR, caused by different triggering events. In current LTE wireless communication system, when a new UL data which is received by upper layers arrives at the transmission buffer and the transmission buffer is empty (i.e. there is no data available for transmission in the transmission buffer), the mobile communications device will trigger a regular BSR to be transmitted to the cellular station of the service network.
Moreover, in current LTE wireless communication system, in addition to normal human-to-human (H2H) communications, machine type communication (MTC) is further provided. MTC is a Machine-to-Machine communication, also referred to as the Internet of Things (TOT), which concept is to connect real world objects to the Internet via the embedded short range mobile transceiver using the radio-frequency identification (RFID) for automatic recognition and information interconnecting and sharing for all of the objects.
For MTC applications, MTC devices usually only transmit small size data, but a large amount of MTC devices causes the small size data accumulated which leads to a large amount of regular BSR may be triggered (and may followed by a scheduling request triggered by the regular BSR) during the transmission of the MTC data, especially for those data which need to be transmitted periodically if current BSR triggering scheme is applied. This may bring an increase in the signaling overhead and decrease the system overall performance since only small size data is required to be transmitted.